首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8981篇
  免费   1646篇
  国内免费   934篇
化学   5984篇
晶体学   86篇
力学   730篇
综合类   65篇
数学   1133篇
物理学   3563篇
  2024年   39篇
  2023年   183篇
  2022年   307篇
  2021年   343篇
  2020年   347篇
  2019年   321篇
  2018年   294篇
  2017年   294篇
  2016年   433篇
  2015年   426篇
  2014年   467篇
  2013年   646篇
  2012年   757篇
  2011年   829篇
  2010年   553篇
  2009年   529篇
  2008年   613篇
  2007年   478篇
  2006年   519篇
  2005年   378篇
  2004年   317篇
  2003年   252篇
  2002年   235篇
  2001年   202篇
  2000年   192篇
  1999年   192篇
  1998年   182篇
  1997年   175篇
  1996年   174篇
  1995年   141篇
  1994年   127篇
  1993年   117篇
  1992年   93篇
  1991年   69篇
  1990年   75篇
  1989年   61篇
  1988年   44篇
  1987年   34篇
  1986年   36篇
  1985年   24篇
  1984年   18篇
  1983年   14篇
  1982年   16篇
  1981年   3篇
  1980年   7篇
  1979年   2篇
  1975年   1篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
After listening to a sound that is presented repeatedly, subjects report hearing different transforms of the original sound. The frequency of reported transforms is a sensitive index of some speech disorders as well as cognitive flexibility in aging. In this paper, we propose and investigate quantitative measures that characterize the dynamics of this phenomenon, known as the verbal transformation effect. In particular, we show that the distribution of the dwell time, the time spent perceiving a string of a given phonemic form before switching to another form, obeys a power law for normal subjects with an exponent valued between 1 and 2. This result suggests that within this paradigm there is no characteristic time scale for the perceptual process. Additionally, we analyze the correlation properties of the transforms. We suggest that the complexity measures and techniques introduced here might be useful diagnostic tools for a number of speech and cognitive disorders. (c) 1995 American Institute of Physics.  相似文献   
72.
We present an algorithm for numerically computing an absolutely continuous invariant measure associated with a piecewiseC 2 expanding mappingS: on a bounded region R N. The method is based on the Galerkin projection principle for solving an operator equation in a Banach space. With the help of the modern notion of functions of bounded variation in multidimension, we prove the convergence of the algorithm.  相似文献   
73.
74.
75.
用维宝康治疗小儿缺锌综合征98例,结果表明,服用维宝康一个疗程后,患者临床症状明显改善发锌值升高,总有效率为96%,未见毒副作用,是较好的补锌制剂。  相似文献   
76.
77.
Converse theorems for multidimensional Kantorovich operators   总被引:4,自引:0,他引:4  
L p [0, l]. . . - .

Supported by National Science Foundation, Zhejiang Provincial Science Foundation of China, and Alexander von Humboldt Foundation of Germany.  相似文献   
78.
79.
Generalized elasticity theory of quasicrystals   总被引:1,自引:0,他引:1  
  相似文献   
80.
With the development of transgenic crops, regulations to label the genetically modified organisms (GMOs) and their derived products have been issued in many countries. Polymerase chain reaction (PCR) methods are thought to be reliable and useful techniques for qualitative and quantitative detection of GMOs. These methods are generally needed to amplify the transgene and compare the amplified results with that of a corresponding reference gene to get the reliable results. Specific primers were developed for the rapeseed (Brassica napus), high-mobility-group protein I/Y(HMG-I/Y) single-copy gene and PCR cycling conditions suitable for the use of this sequence as an endogenous reference gene in both qualitative and quantitative PCR assays. Both methods were assayed with 15 different rapeseed varieties, and identical amplified products were obtained with all of them. No amplification was observed when templates were the DNA samples from the other species of Brassica genus or other species, such as broccoli, stem mustard, cauliflower, Chinese cabbage, cabbage, sprouts, Arabidopsis thaliana, carrot, tobacco, soybean, mung bean, tomato, pepper, eggplant, plum, wheat, maize, barley, rice, lupine, and sunflower. This system was specific for rapeseed. Limits of detection and quantitation in qualitative and quantitative PCR systems were about 13 pg DNA (about 10 haploid genomes) and about 1.3 pg DNA (about 1 haploid genome), respectively. To further test the feasibility of this HMG-I/Y gene as an endogenous reference gene, samples containing transgenic rapeseed GT73 with the inserted glyphosate oxidoreductase (GOX) gene were quantitated. These demonstrated that the endogenous PCR detection systems were applicable to the qualitative and quantitative detection of transgenic rapeseed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号